Dargle Flood Defence Scheme

Bray is a town in Co. Wicklow, Ireland which was identified by the Office of Public Works as an urban area at periodic risk of flooding. Bray Town Council and Wicklow County Council developed the River Dargle Flood Defence Scheme to protect life and property at risk from flooding from both severe high tides and river flooding due to extreme rainfall events.

Gavin & Doherty Geosolutions was commissioned to complete the design of the flood defences along Ravenswell Road and Seapoint Court in Bray. Furthermore GDG were asked to develop conceptual design solutions for several other areas of the river. The defences that are required in these areas are a combination of flood barriers to contain the river and a flood relief channel to relieve flood waters that may threaten the nearby low-lying residential areas.

Scope of Work:

Gavin & Doherty Geosolutions was tasked with designing the flood defences along the tidal zone of the River Dargle, a largely residential area just north of the centre of Bray Town. GDG is responsible for preparing detailed designs of the defences and ensuring that they are fit for purpose and in accordance with the requirements of the project’s Environmental Impact Statement. Initial activities at the outset of the project included undertaking site investigations for geotechnical parameters and utilities investigations to define the services in the area.

To provide the defences along this part of the river a combination of retaining structures were required. The detailed design incorporates:

Reinforced Earth Embankments

Anchored Sheet Piled Walls

Secant Pile Walls

Reinforced Concrete Retaining Walls

Composite Structures (Tying old masonry walls into new Reinforced Concrete structure to provide a gravity wall)

Gabion Based Structures and Stone Revetments

The detail design makes allowance for a number of pre-existing utilities, in particular two large diameter sewers. Other site constraints included interfaces with adjacent properties and the condition of existing retaining walls where underpinning was designed to support the walls during temporary works.

The project was constructed within a tight schedule defined by the fisheries season and on-site quality control was deemed essential.

A highly reactive approach to construction variations that arose on site was required to ensure the project progressed on time and in budget.